Dec. 03, 2012

The Australian green tree frog has big eyes, a friendly demeanor, and a bit of a pot belly, all of which bring to mind certain traits of Muppet star Kermit the Frog. Both are popular human companions, too, the former as a pet, the latter as a familiar character of television shows and movies. And so, I began to wonder what else the puppet and his Australian cousin might, or might not, have in common.

I'll begin with some obvious differences. The Australian green tree frog (Litoria caerulea) is plump, most notably around the neck and trunk, whereas Kermit, despite his egg-shaped belly, is rather spindly-looking. When it comes to overall size, however, the green tree frog is smaller, being about two to four inches in length, whereas the television version of Kermit presumably is around two feet in height. In addition, Kermit is bipedal and walks, while his cousin hops, and while Kermit can talk, the green tree frog calls “wark, wark, wark” and tends to squeak when touched.

Each frog has a distinct origin and distribution, and yet similar patterns can be seen, namely the use of humans as a means of introduction to new places. The green tree frog, for instance, is native to Australia and New Guinea but was introduced to New Zealand and the United States by humans. Kermit appears to have been born somewhere in the Deep South in the United States (though the precise location is uncertain) and was later introduced, by humans, to countries worldwide.

With certain behavioral characteristics, we again see differences and similarities. For example, the Australian green tree frog, as its name suggests, is arboreal. The closest Kermit seems to come to trees is when he plays his banjo while sitting on a log (he has been known to pluck a mean rendition of the Deliverance duel on the banjo). Of course, that log that Kermit likes so much is in a swamp, the type of habitat in which he claims to have been born and raised (he recalls his fondness for the swamp in his lesser-known 2002 film, Kermit: The Swamp Years). The green tree frog enjoy moist habitats, too, being especially fond of standing water, including that of not only swamps and ponds but also cisterns and toilets.

In fact, welcome or not, the Australian green tree frog is just as much a part of peoples' households as is Kermit. Both are popular for their endearing appearance, but the green tree frog is especially likable because of its tame, docile manner. It is also long-lived, surviving one or two decades (shorter than Kermit's “life span”), and is relatively easy to take care of, though without trees to climb for exercise and with overzealous feeding, it has a tendency to become obese in captivity. Kermit, on the other hand, has maintained the same physique all his life, despite having spent quite a lot of time with humans.

Another interesting point of comparison centers on each frog's skin. Kermit is perpetually bright green -- the basis for his lament “it's not easy bein' green” -- but the green tree frog may be bright or dull green or even bluish in color. It also has a white underside and sometimes has small white spots on its back.

Kermit's skin also seems remarkably dry for an amphibian. The Australian green tree frog, by contrast, has waxy skin that secretes a substance with antimicrobial properties. Its skin secretions also contain a compound known as caerulein (ceruletide), which is used in humans to treat partial or complete obstruction of the intestine.

Of course, in the end, each frog has its own niche. Kermit's is in entertainment, and the Australian green tree frog is found generally in wet, humid areas with trees and in home aquariums.

About Kara Rogers

Kara is a freelance science writer and senior editor of biomedical sciences at Encyclopaedia Britannica, Inc. She is the author of Out of Nature: Why Drugs From Plants Matter to the Future of Humanity (University of Arizona Press, 2012).

The views expressed are those of the author and are not necessarily those of Science Friday.